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This study examines the patterns of diversity within three natural snowbeds and one
manipulated snowbed at Alexandra Fiord, Ellesmere Island in the Canadian High Arctic.
Recent predictions of climate change in the Arctic suggest that not only will temperature
increase, but also snowmelt will be earlier leading to a longer growing season. Experimental
manipulations of snowmelt were begun in 1992 in a late-lying snowbed in order to determine
the response of species to longer and shorter growing seasons.
To measure the biomass of each species within the manipulated snowbed without
destructively harvesting the vegetation, the point quadrat method of estimating total species area
(TSA) was employed. Simple linear regressions of TSA and biomass for each species were
constructed and were used to estimate biomass from only TSA data. For most species the
variance explained (R²) was very high ranging, from 0.311 to 0.943. When diversity indices
were calculated, there was essentially no difference between the values as calculated from real
or from estimated biomass. The best fitting relative abundance distribution model for each
quadrat was also consistent, regardless of whether actual or estimated biomass was used.
Therefore, this method offers an efficient alternative to destructively harvesting a large number
of quadrats for relatively simple communities and allows a non-destructive means to follow
biomass changes in permanent quadrats over time.
Ordination using redundancy analysis (RDA) showed that gradients of biomass, soil pH,
moss cover and snow meltdate were found strongly related to the community structure within
the natural and manipulated snowbeds. Total quadrat biomass was found to be the most
important variable in the RDA at explaining the variation of species data and was significantly
related to diversity. All measures of alpha diversity decreased with increasing biomass. When
the three natural snowbed communities are included with other arctic communities, a hump
shaped relation between species richness and biomass is observed, with a peak in diversity at
moderate biomass. These results offer indirect evidence that biological interactions, namely
competition, may be important in structuring these high arctic communities.
Patterns of alpha diversity within the natural snowbeds were not significantly related to
snowmelt, although there were more graminoid species in the earliest melting plots, with the
longest growing season, and more forbs species in the last plots to melt. The manipulated
snowbed, with snow removal, snow addition and control plots, also had more graminoid species
in the plots where snow had been removed. The lowest species richness was found in the snow
addition plots while greatest richness was found in the removal plots. However, evenness
increased in both the addition and removal plots. This suggests that the graminoid species will
likely become more abundant in the short term if the growing season length increases as a result
of climate change. The importance of this work is that it is the first evidence that snowmelt
changes will alter the structure of arctic communities, although more research is necessary to
determine the resultant functional changes that will likely accompany structural changes in these
and other arctic tundra ecosystems.